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首页> 外文期刊>Journal of Molecular Biology >Millisecond time-resolved changes occurring in Ca2+-regulated myosin filaments upon relaxation.
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Millisecond time-resolved changes occurring in Ca2+-regulated myosin filaments upon relaxation.

机译：放松后，Ca2 +调节的肌球蛋白丝中发生的毫秒时间分辨变化。

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摘要

Contraction of many muscles is activated in part by the binding of Ca(2+) to, or phosphorylation of, the myosin heads on the surface of the thick filaments. In relaxed muscle, the myosin heads are helically ordered and undergo minimal interaction with actin. On Ca(2+) binding or phosphorylation, the head array becomes disordered, reflecting breakage of the head-head and other interactions that underlie the ordered structure. Loosening of the heads from the filament surface enables them to interact with actin filaments, bringing about contraction. On relaxation, the heads return to their ordered positions on the filament backbone. In scallop striated adductor muscle, the disordering that takes place on Ca(2+) binding occurs on the millisecond time scale, suggesting that it is a key element of muscle activation. Here we have studied the reverse process. Using time-resolved negative staining electron microscopy, we show that the rate of reordering on removal of Ca(2+) also occurs on the same physiologicaltime scale. Direct observation of images together with analysis of their Fourier transforms shows that activated heads regain their axial ordering within 20 ms and become ordered in their final helical positions within 50 ms. This rapid reordering suggests that reformation of the ordered structure, and the head-head and other interactions that underlie it, is a critical element of the relaxation process.
机译：许多肌肉的收缩在一定程度上是由Ca（2+）结合到粗丝表面上的肌球蛋白头部或磷酸化的。在松弛的肌肉中，肌球蛋白的头部呈螺旋状排列，并且与肌动蛋白的相互作用最小。在Ca（2+）结合或磷酸化上，头部阵列变得无序，反映了头部的断裂以及构成有序结构的其他相互作用。头部从细丝表面松动，使它们可以与肌动蛋白细丝相互作用，从而引起收缩。放松后，头部恢复到其在细丝骨架上的有序位置。在扇贝纹状的内收肌中，发生在Ca（2+）结合上的无序发生在毫秒级，这表明它是肌肉激活的关键因素。在这里，我们研究了反向过程。使用时间分辨的负染色电子显微镜，我们表明去除Ca（2+）的重新排序的速度也发生在相同的生理时间尺度上。对图像的直接观察以及对其傅立叶变换的分析表明，激活的磁头在20 ms内恢复了轴向顺序，并在50 ms内在其最终螺旋位置变为有序。这种快速的重新排序表明，对有序结构以及其基础的头部和其他相互作用的重塑是松弛过程的关键要素。

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